This invention is related to a method of cultivating kava plants, and in particular, to a cultivation method that results in rootstock and lateral roots of improved size while also simplifying planting and harvesting. The invention is also related to improved methods of generating seedlings which can be used to cultivate kava plants.
Kava plants, a type of pepper plant also known as Piper methysticum, are generally found in Polynesia, Melanesia, and Micronesia. The kava plant contains high concentrations of kavalactones, including kavain, methysticin, and yangonin, and has been used as an herbal medicine. The prized part of the kava plant is the root system because it contains the highest concentrations of the active ingredients, the kavalactones. The concentrations of the individual kavalactones can vary depending on the particular kava cultivar. General information about kava plants can be found in Vincent Lebot, et al., xe2x80x9cKava The Pacific Elixir, The Definitive Guide to its Ethnobotany. History, and Chemistryxe2x80x9d, Inner Traditions Intl. Ltd. (March 1997).
The root system of the kava plant consists of two major parts: (1) the rootstock or stump or corm, and (2) the lateral roots. The above-ground stems grow upward from the rootstock, and the below-ground lateral roots grow out radially from the rootstock. On average, the concentrations of the kavalactones in the lateral roots are two to three times higher than in the rootstock. Thus, the lateral roots are more commercially valuable by weight then the rootstock.
After a kava plant is harvested, the root is typically dried and then ground to a powder. The powder can be packaged into capsules or other forms and can be mixed with water to form a beverage. The effects of ingesting kava root extract will vary from person to person, and also on the manner in which the kava is ingested, such as via capsules, tea, etc. Common effects include a state of relaxation and a reduction in muscle tenseness. Kava root has been used to help sufferers of insomnia. It can also produce a mild state of euphoria.
Kava plants grow best in deep, friable, well-drained soils that are rich in organic matter. The plant is very nutrient demanding and the highest yields are generally obtained in silica-clay soils having a pH of 5.5 to 6.5. Historically, several specialized techniques have been developed by kava growers to improve the yield or appearance of the root system. In one technique, a stem cutting is placed into a hollow tree trunk and the kava is allowed to grow inside of the trunk. Although this technique can produce high quality rootstock and lateral roots, it suffers from low yields. The harvest, post-harvest, and replanting cycle time for this technique is also lengthy. In an alternative technique, used in the islands of the Pacific where there are relatively young volcanic lava flows which have not yet weathered into deep soils, such as Samoa, kava is grown in pits which are filled with organic matter. This technique also suffers from a long harvest, post-harvest, and replanting cycle time.
Conventional commercial cultivation of kava typically involves digging a series of holes in clay soil into which kava seedlings are planted. Although appearing simple, in practice this is generally a time-consuming and expensive process. The planted seedlings must mature for one and one-half years or more in order for there to be a sufficient concentration and proportion of kavalactones in the roots to provide roots which are commercially valuable enough to harvest. During this growth period, the plants are exposed to nematodes and insects and infestations are common. Pesticides and herbicides are therefore often used to reduce damage caused by these pests.
After the kava plants have matured, they are harvested for their roots. Conventional harvesting is done by hand using a flat bladed digging fork pushed around and under the rootstcok and roots. Modern techniques use mechanized equipment, such as a backhoe, to dig the rootstock and lateral roots out of the ground. Full excavation is a drawn-out process and can often take an hour or more per-plant because the lateral roots can penetrate two to three meters into the ground. Mechanical excavation can also damage the roots, particularly the smaller and more valuable lateral roots. The time required to excavate a plant can be reduced at the expense of reducing the amount of the root system, and the amount of lateral roots in particular, which is excavated for harvest. However, such a solution also reduces the value of the harvested plant because the loss is concentrated in the kavalactone rich lateral roots. Processing time is further increased because the clay soil can be relatively difficult to remove from the roots unless careful cleaning techniques are used.
Accordingly, it would be advantageous to provide an improved method of cultivating kava plants as an agricultural root crop which provides for a high rate of growth to minimize growth cycle time while also producing high concentrations of kavalactones.
It would be a further advantage if such a method would permit easy excavation and cleaning to minimize harvest cycle time and post-harvest processing time and further enable rapid planting of young kava plants after excavation of the mature kava plants to minimize the replanting cycle time.
It would be yet a further advantage if such a method resulted in reduced damage to the plants from pests and fungus, and therefore permitted commercially suitable crops to be grown with reduced and preferably no use of pesticides and herbicides.
Kava plants do not produce fruit or seeds and are propagated via cuttings from a mother plant. Thus, in order to farm kava plants in quantity, cuttings of the kava stalks need to be transplanted. Conventional techniques for generating kava seedlings are based on directly transplanting the cuttings and the typical success rate is less than 50%. Accordingly, it would be advantageous to provide an improved technique of generating kava plant seedlings. It would be a further advantage if such a method stimulated production of lateral root mass and increased kavalactone concentration in the mother plant.
These and other advantages are achieved through the use of a new method for kava growth which utilizes a growth medium for the rootstock and lateral roots that permits easy and fast planting and harvesting. According to one aspect of the invention, a growth medium is formed in which kava plants are grown in mounds or mounded rows which are between about 12 inches and 40 inches in height, and preferably, between 18-30 inches. By providing such unconventionally high mounds or mounded rows, a robust and extensive root growth is promoted. Several different compositions for the growth medium can be used depending on the environment in which the kava is to be grown.
A kava seedling is planted in each mound or several seedlings are planted in a spaced-apart arrangement in the mounded rows. When a plant has matured, it is preferably harvested by using a forklift with a suitable fork or other appropriate equipment to uproot the plant and lift it out of the mound. The plant is shaken to remove the loose soil and the roots are cleaned by immersion in tanks of water and preferably with high pressure jets of water. The entire plant can then be placed in a refrigerated container and transported for subsequent processing.
Use of the present methods provide a significant increase in total size of the harvested root structure, and particularly a significant increase in the amount of lateral roots relative to rootstock which is harvested. A concurrent increase in net concentration of kavalactones as a percentage of harvested root bio-mass is also achieved. As a result, commercially superior roots can be obtained in a growth period which is four to six months shorter than the conventional growth period.
Advantageously, through use of this method, harvesting and replanting are also simplified and the harvest cycle time is greatly accelerated. Unlike conventional techniques where the kava plant must be carefully and laboriously dug from the ground by hand or with the aid of a backhoe to harvest the roots, the raised mounds or mounded rows allow easy access to the root structure using a hydraulic lifting fork which can be inserted into the mound at or near ground level and then lifted to excavate the plant. Further, the mounds or mounded rows can easily be reformed after harvesting to allow subsequent planting of another kava seeding.
According to a further aspect of the invention, an improved technique for producing seedlings from a kava plant is disclosed in which the apical tip of a kava plant stem is cut. This generates subsequent growth of buds in the uncut stem which can be later harvested to provide a large number of seedlings for subsequent planting. Advantageously, the initial cut and subsequent new-growth harvest also stimulates, at least to some extent, the production of lateral root mass and an increase in kavalactone concentrations in the root of the mother plant a period of time after the stem is harvested for seedlings. As a result, the generation and harvesting of seedlings does not reduce the commercial value of the root mass in the mother plant and can, in some circumstances, even enhance it.